(1) Field of the Invention
The present invention relates to an information retrieval apparatus which carries out information retrieval using association dictionaries which memorize associations between words included in information stored in a database.
(2) Description of the Related Art
Conventional methods for creating an association dictionary to be used for database retrieval include, for example, manually creating an association dictionary by examining relationships between words included in information stored in a database, and automatically creating an association dictionary using information about apparition frequency of words in an electronic text. As to a method of automatically creating an association dictionary based on the relationships between the words, various methods are under development.
One of the methods for using the association dictionaries thus created is, for example, in the case where information retrieval is performed by an information retrieval apparatus using a search keyword and no results are obtained, a keyword related to the search keyword is extracted using an association dictionary and information is retrieved again using the extracted keyword.
As such information retrieval apparatus, a text processor is disclosed as such that provides, as a support for an input of a search keyword, plural association dictionaries that store related words, allows the user to select one association dictionary among them for information retrieval, obtains, from the selected association dictionary, a related word relating to a keyword inputted by the user, and displays the related word (see reference to Japanese Laid-Open Application No. 10-134075). Also, an association dictionary creating apparatus is also disclosed as such that establishes a customized association dictionary to meet personal needs, and after an input of a search keyword, searches the search keyword in the customized association dictionary, and in the case where the search keyword is not found in the customized association dictionary, obtains one or more related words relating to the search keyword from an integrated association dictionary storing all of keywords, and presents the user with the related word (see reference to Japanese Laid-Open Application No. 2000-348042).